<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var a = new Set([2,3,4,2]); 
        console.log(a);  //{2, 3, 4} 互异性
        console.log(a[0]);//undefined 无序性
        var c = new Set([2,3,4]);
        var b = new Set([4,2,3]);
        var d = a;
        console.log(d==a);
    </script>
</body>
</html>